The present invention pertains to a remix hopper and transfer device for concrete and similar materials and, more particularly, to a compact mobile device particularly adapted for use in confined areas such as tunnel construction.
The prior art is repleat with devices designed and constructed to facilitate the placement of concrete at construction sites and to simultaneously provide temporary storage or surge capability to allow delivered batches of concrete to be stored for short periods until transferred for placement. Such devices also typically include an agitator to remix or retemper the concrete while it is being held in the storage bin on the device. These devices are also often designed for mobile travel such as by mounting the device on a rail carriage for operation on a track or on a wheeled chassis which may or may not be self-propelled.
In order to accommodate the manner in which ready mixed concrete is delivered to a construction site, the nature of the construction activity, and the manner in which the concrete is ultimately placed in the structure, remix hoppers or surge bins include a variety of devices to accommodate loading and a similar variety of devices to facilitate discharge. A typical application for a mobile surge bin is in tunnel construction. The bins typically comprise a conventional elongate open-topped body mounted on a frame which, in turn, is supported on rubber tires or a rail wheel carriage. However, the bin may also be temporarily used in a stationary position supported on its subframe and without any wheeled support. The bin may include a remixing and transfer agitator typically including a series of paddles rotatable on a longitudinal axis to move the concrete toward the rear end for discharge through a vertically openable gate, the position of which can be varied to meter discharge. The open-topped bin may also be pivotally attached to the carriage near the discharge gate to allow the front end of the bin to be lifted to facilitate discharge. A belt conveyor may also be attached to the rear of the device to receive at its lower end concrete discharged through the gate and to carry the concrete upwardly at an angle to an elevated conveyor discharge end. This allows concrete to be placed at a substantially higher level than may be accommodated by the discharge gate. For example, the higher discharge may be required in order to place concrete into the hopper feeding a concrete pump or to deliver concrete to another mobile surge bin for use in shuttle delivery, as in the construction of a tunnel.
Another known construction for a surge bin eliminates the need for an elevating discharge belt conveyor by utilizing a lift mechanism which raises the entire bin vertically from the chassis or carriage to place the discharge gate at an elevated position. Such lift mechanisms may also provide corresponding tilt to the bin to further facilitate rearward movement and discharge of the concrete. This device is shown in U.S. Pat. No. 4,441,820 granted to the inventor of the subject invention.
Both of the foregoing types of surge bins may be fed or supplied concrete by ready mix carriage vehicles which simply dump directly over the open upper peripheral edge of the bin into the open interior. Alternately, concrete may be supplied to the surge bin by a belt conveyor attached to the front end of the bin and having an upper discharge end positioned above the open interior and a lower feed end extending longitudinally forward of the apparatus. One major disadvantage of surge bins which must be lifted to discharge is that their operation is cyclic, thus preventing loading during discharge and vice versa.
Two primary factors in tunnel construction, particularly in smaller diameter confined tunnels having, for example, diameters of 12 feet or less, make use of any of the foregoing prior art types of mobile surge bins impractical or impossible. First of all, the inherent low head room will not accommodate tilt or lift mechanisms which raise the surge bin body vertically above the supporting carriage or chassis. Second, longitudinal space along the tunnel construction site is typically limited and, therefore, long belt conveyors used both for discharge and for loading the surge bin add significantly to the length of required equipment space and are, therefore, undesirable.
Notwithstanding the inherent limitations imposed by tunnel construction in relatively small diameter passages, mobile remixing surge bins can provide a cost effective and operationally satisfactory system if the problems related to height and length space limitations can be overcome while still allowing the surge bins to be loaded and discharged at approximately the level of their peripheral upper edges. This includes the need to provide shuttle transfer of concrete from one surge bin to the next where lateral space constraints preclude side-by-side passage of vehicles. Any alternate means which may be provided to load and/or unload the surge bin must be at least as efficient and effective as prior art devices. Also, the device should be able to be effectively loaded from a horizontal concrete carrier, such as a Moran car, commonly used in tunnel construction.